Thread overwrap mechanism

ABSTRACT

Mechanism usable with a book cleat sewer which is actuatable upon completion of thread sewing across a cleat in the spine of a book being sewn to positively ensure thread over-wrap completely about the last end sheet in the cleat being sewn.

United States Patent Streeter Mar. 19, 1974 THREAD OVERWRAP MECHANISM2,800,095 7/1957 Schramm 112/21 [75] Inventor: Daniel I. Streeter,Glastonbury,

Conn- Primary Examiner-Geo. V. Larkin [73] Assigneez The SmythManufacturing Attorney, Agent, or Firm'-Prutzman, Hayes, Kalb &

Company, Bloomfield, Conn. chlton [22] Filed: May 24, 1973 Appl. No.:363,666

us. c1. 112/21 1m. (:1 B42b 1/02 Field of Search 11/1 R, 1 CP; 112/21,22

References Cited UNITED STATES PATENTS 7/l9l7 Bischof 1. 112/21 [57]ABSTRACT Mechanism usable with a book cleat sewer which is actuatableupon completion of thread sewing across a cleat in the spine of a bookbeing sewn to positively ensure thread over-wrap completely about thelast end sheet in the cleat being sewn.

12 Claims, 8 Drawing Figures PATENT) MR 1 9 ISM SHEET 5 [IF 6 1 THREADOVERWRAP MECHANISM This invention relates to machines for sewing cleatson a spine of a book and particularly concerns the sewing head portionof such a machine.

A primary object of this invention is to provide a cleat sewing machinehaving a new and improved thread over-wrap machanism which positivelyensures thread wrap about the end sheets of each cleat to be sewn on aspineof the book.

Another object of this invention is to provide such a new and improvedthread over-wrap mechanism which not only significantly improves thequality of a cleat sewn book, but consumes virtually no added timerequirements relative to a conventional cleat sewing operation andutilizes a minimum number of operating components.

Other objects will be in part obvious and in part pointed out in moredetail hereinafter.

A better understanding of the objects, advantages, features, propertiesand relationships of the invention will be obtained from the followingdetailed description and accompanying drawings which set forth anillustrative embodiment and are indicative of the way in which theprinciples of this invention is employed.

In the drawings:

FIG. 1 is an isometric view, partly broken away, of a cleat sewerincorporating this invention;

FIG. 2 is a plan view of a portion of a sewing head of the cleat sewerof FIG. 1;

FIG. 3 is an end view, partly broken away, of the sewing head of FIG. 2;

FIG. 4 is an enlarged partial plan view, partly broken away, of thesewing head of FIG- 2;

FIG. 5 is. an isometric view showing part of a book spine having a pairof sewn cleats;

FIG. 6 is a schematic illustration of the path of needle movement duringsewing of a cleat;

FIG. 7 is a side view, partly broken away and partly in section, of aneedle rod shown from an end of the sewing head of FIG. 1; and

FIG. 8 is a schematic illustration of a portion of a control system forthe sewing head.

Referring in detail to the drawings, a sewing head 10 of a cleat sewer12 is shown incorporating a preferred embodiment of this invention. Asuitable book clamp 14 and indexing means, not shown, are provided forholding and indexing a book.16 to be sewn. The book 16 is transportedfrom a book loading and unloading station 17 on a slide 18 in adirection parallel to the spine of the book 16 through a saw station 20,wherein cleats such as at 22 are formed in the spine 23 of the book 16,and a sew station 24 for sewing the cleats. As seen in FIG. 1, the bookspine 23 is fed from the book loading and unloading station 17 (whereinthe book 16 is shown in broken lines) with the spine 23 down anddisposed in a plane overlying the saw and sew stations and 24.Thereafter, the book is further advanced to an extreme limit positionand subsequently returned to station 17 for unloading.

The sewing head 10 has a needle rod 26 (best seen in FIG. 7) operativelymounted on a spindle 28. The spindle 28 is fixed on a pair of shafts 30and 32 extending perpendicular to the needle rod 26 as best seen inFIGS. 2 and 4 with the shafts 30, 32 mounted for reciprocable movementon spaced end plates 34 and 36 secured to side plates 38 and 40 of aspindle carriage 42.

The spindle carriage 42 is in turn supported for reciprocable movementon a cross shaft 44 fixed to a stationary frame 46 and a cam shaft 48suitably mounted on that frame 46 for rotation.

The spindle 28 is reciprocable relative to and parallel to the carriageside plates38, for reciprocating a needle 50 of the needle rod 26 in adirection normal to the longitudinal axis of the needle rod 26. Thisdirection of movement is hereafter called a longitudinal direction whichis to be understood to be parallel to the longitudinally extending spine23 of the book 16 which is to be positioned by book clamp 14 inoverlying relation to the needle rod 26 of the spindle 28. Each cleat 22is sequentially indexed into overlying parallel relation to the spindle28 for sewing by the needle 50. As seen in FIG. 5, each cleat 22 isdefined by inwardly sloping pairs of saw cuts 52 and 54 suitably formedin the book spine 23 at saw station 20. The saw cuts or slits 52, 54extend laterally across book spine 23.

To reciprocate spindle 28 in the longitudinal direction parallel to thecarriage side plates 38 and 40, the shafts 30 and 32 arefixed to andinterconnected by bracket 56 having a cam follower 58 which will beunderstood to engage a contoured internal cam path, not shown, on aspindle cam 60. The latter is fixed to a cam drive assembly 62 mountedon cam shaft 48 between the carriage side plates 38 and 40. Cam driveassembly 62 is splined to cam shaft 48 for transmitting rotary motionupon rotation of cam shaft 48'while permitting movement of cam driveassembly 62 axially of cam shaft 48 upon operation of a four way valve64 controlling a reversible sewing head feed cylinder 66 which isconnected to a suitable source of power, not shown,

such as compressed air. The cylinder 66 has an extendible andretractable piston rod 68 (FIG. 4) fixed to a bracket 70 which will beunderstood to be secured to end plate 36 of carriage 42 forreciprocating it on frame 46. Carriage 42 is sequentially indexedintermittently in a feed direction. The feed direction of carriage 42(and drive cam assembly 62) is from left to right, as

viewed in FIGS. 24. A rack and pawl escapement '71 (FIG. 3) betweenframe 46 and spindle 28 cooperates with feed cylinder '66 in the feeddirection to provide controlled intermittent indexing of carriage 42 intimed relation to cam shaft rotation and longitudinal movements ofspindle 28 to provide a desired sewing pattern. It will be understoodthat cam shaft 48 extends through oversize openings, not shown, withinside plates 38 and 40 of carriage 42, permitting its lateral movementrelative and parallel to cam shaft 48.

To also provide limited needle movement relative to the carriage 42itself, crosswise to the book spine 23 to be sewn, needle rod 26 isshown (FIG. 7) drivingly con nected by a depending lug '72 of a tubularconnector 74 to a spindle oscillating block 76 supported forreciprocating movement on a pair of shafts 78 and 80 (FIGS. 2 and 4) inparallel overlying relation to end plates 34 and 36. As described morespecifically below, needle rod 26 is telescopically mounted withintubular connector 74 and is normally driven in unison with spindleoscillating block 76 and spindle 28. Needle rod 26 is provided asuitable bearing 81 on spindle 28 which also permits needle rod 26 tomove axially relative to spindle 28. To reciprocate spindle 28 andneedle rod 26in unison relative to carriage 42, a follower arm 82,integrally formed on spindle oscillating block 76, is provided with acam follower 84 (FIG. 3) received for following movement in a cam path86 of a spindle barrel cam 88 fixed to cam drive assembly 62 for movingneedle 50 relative to spindle carriage 42 and crosswise to book spine 23to be sewn.

Spindle oscillating block 76 is provided with a slot 90, extending inthe so-called longitudinal direction, for receiving depending lug 72 oftubular connector 74 within which needle rod 26 is mounted. Suchconstruction provides for driving both spindle oscillating block 76 andneedle rod 26 in unison, axially of needle rod 26 and transversely tobook spine 23, while permitting following movement of needle rod 26longitudinally and also angularly of book spine 23.

To prove yet another motion, more specifically, an angular motion toneedle 50, a needle rod gear 92 is mounted on an end of needle rod 26for meshing engagement with an intermediate gear 94 (FIG. 7) mounted ona spindle side plate 96. Gear 94 in turn engages rack 98 drivinglyconnected by connecting rod 100 to a cam follower 102 in engagement withan internal cam path, not shown, on a rack cam 104 fixed to cam driveassembly 62 on cam shaft 48. Reciprocable movements of rack 98 infollowing relation to rack cam 104 and in timed relation to the othermotion producing cams 60 and 88 provides for desired angular movementsof needle 50 in opposite angular directions about the axis of needle rod26 during cleat sewing, to ensure needle alignment with the angularlydisposed saw cuts 52, 54 of cleat 22, and permits needle 50 to beinserted into and withdrawn from book spine 23.

To determine thickness of the book being sewn for purposes ofterminating the sew cycle on a cleat, a sensor block air cylinder 106 ismounted on stationary frame 46 of sewing head 10 with a piston rod 108which drivingly connects with and positions a sensor block 110, movablymounted on shaft 44 of frame 46. Cylinder 106 positions block 110against a movable jaw 112 of book clamp 14 upon it being suitablydogged, by means not shown, in position for the sewing of each cleat.With sensor block 110 positioned in preselected relation to book clamp14 and in fixed relation to carriage 42, a predetermined indication ofthe thickness of each book 16 being sewn is thus provided, and a switchactuator 114 is mounted on sensor block 110 for engaging a limit switch9LS to commence termination of the sewing cycle for each cleat 22 asspecifically described below.

The three described cams 60, 88 and 104 and their driving connections toneedle rod 26 accordingly provide a complex compound motion forprogressively sewing each cleat in spine 23 of book 16 in successivesections proceeding crosswise across the spine of the book, preferablyin a progressive series of so-called figure 8 patterns. As best seen inFIG. 6 (which is to be understood as a bottom view projection of thecleat being sewn), needle 50 starts from a rest position A with carriage42 positioned adjacent frame side plate 116 and with spindle 28 adjacentcarriage end plate 34 to align needle 50 with the leading saw cut 52.

Driven by spindle barrel cam 88, needle 50 will move crosswise towardbook spine 23 into home position A and thereafter longitudinally outsidecleat 22 between saw cuts 52 and 54 under the influence of spindle cam60 while needle 50 is also being rotated, by the modifying action of therack and gear train drive connection between rack cam 104 and needle rod26, into a position parallel with line XX (FIG. 5) in entering relationto trailing saw cut 54.

A progressive sewing pattern then continues as an advancing figure 8 asseen in FIG. 6 across spine 23 between saw cuts 52 and 54. Longitudinalneedle movement is provided by spindle cam 60 and modified by rack cam104. The rack and pawl escapement 71, such as seen in FIG. 3, will beunderstood to cooperate with spindle cam 60 and the reversible feedcylinder 66 to intermittently feed carriage 42 and cam drive assembly 62in unison transversely or cross-wise of the book spine. That is,cylinder 66 provides intermittent feeding motion from left to right asviewed in FIG. 6 as controlled by escapement 71 in timed relation torack cam 104 during the time needle 50 is below book 16. The aircylinder feed is modified by the barrel cam 88 to provide a desireddirection and distance of needle travel crosswise of the book.

To initiate termination of the sew cycle near the end of the sewingtraverse of needle 50 across book spine 23, the switch 9LS on carriage42 contacts actuator 114 to condition the sewing head 10 for threadoverwrap in accordance with this invention.

Positive thread overwrap about the last sheet of each cleat 22 isassured by providing a suitable needle rod drive to thrust needle 50through the trailing saw cut 54 and beyond the last end sheet of book 16to positively wrap thread around that last end sheet.

In the specifically illustrated embodiment of this invention, a normallyde-energized air cylinder 118 is provided with a piston rod 120coaxially secured to needle rod 26 as seen in FIG. 7. Spindleoscillating block 76 is drivingly engaged with depending lug 72 oftubular connector 74 which telescopically houses an end of the needlerod 26, and the tubular connector 74 is threadably connected with an endof cylinder 118. Rod 120 of piston 122 is screwed into an end of needlerod 26 and secured by a lock nut 124 within connector 74.

Tubular connector 74 normally serves to impart movement to the needlerod 26 in direct relation to spindle 28, axially of the needle rod 26and crosswise of book 16 being sewn. In the preferred embodiment, adrive pin or dowel 126 is fixed to connector 74 to extend through anelongated slot 128 in needle rod 26 and is normally maintained in sewposition by a compression spring 130 received in cylinder 118 on its rodside urging piston 122 toward the left with dowel 126 in abuttingdriving engagement with needle rod 26 at the right hand side of itselongated slot 128 as viewed in FIG. 7. Spindle 28 (which is in fixedrelation to the tubular connector 74 and its lug) and the needle 50 arethus normally driven directly by the lug 72 as it follows the movementsof the cam follower 84 laterally of the book spine.

As spindle carriage 42 traverses across book spine 23 from its startingor first traversing position, with the needle 50 adjacent the first endsheet of the book 16, to a terminal or second traversing positionestablished by sensor block 110, needle 50 is adjacent the last endsheet to be sewn. With the carriage switch 9LS engaging actuator 114 onframe 46 and with needle 50 approaching needle position B (FIG. 6),e.g., near the end of its sewing traverse, any further lateral feedmovement will be limited to the throw of the needle 50 by the camfollower 84 once needle 50 reaches position B with carriage 42 engagedwith the sensor block 110. Depending on the timing of the arrest ofspindle carriage 42 relative to the needle position upon carriageengagement with sensor block 110, it will be seen that such lateral feedmovement frequently is insuffcient to ensure complete thread overwrap ofthe last sewn end sheet if the normal figure 8 pattern were merelyrepeated. However, in accordance with this invention, cylinder 118 isenergized in response to actuation of switches 9LS and 12LS once needle50 is aligned with trailing saw cut 54 as in position B to di rect airthrough a common supply and exhaust passage 132 into the piston side ofcylinder 118.

As needle 50 is being driven out of trailing saw cut 54 to the right inFIG. 6 by the follower 84, the resilient drivig connection maintainingneedle rod 26 in its normal full line or sew position illustrated inFIG. 7 is overcome, and needle rod 26 is thrust an additional distance a(FIG. 6) further to the right into a thread overwrap position C todepart from the sewing of the normal figure 8 stitch in the abovedescribed advancing repetitive pattern. The needle rod 26 is thusshifted axi ally to the right relative to the spindle 28 through thedisclosed lost motion drive whereby the drive pin 126 is relativelypositioned at the left side of needle rod slot 128. This slot 128 issuitably dimensioned to permit needle 50 to depart a sufficient distancefrom its normal figure 8 stitch to ensure complete thread overwrap aboutthe end sheet without merely backstitching the thread through the endsheet as conventionally done upon return movement of the oscillatingblock 76 and the spindle 28 to the left as viewed in FIG. 7.

. More specifically, a portion of a suitable control circuit isschematically shown in H6. 8 with only certain significant controlsbeing illustrated. Upon being indexed into position at the sew station24, book 16 trips a swith 8LS to energize sewing cycle relay 4CR, whichis held in by its contacts 4CR-2, and opens its contacts 4CR-1 tode-energize indexing relay 2CR which in turn opens its contacts 2CR-l tode-energize solenoid 4SOL to dog book clamp 14 of slide 18 in positionfor sewing. With clamp 14 dogged, limit switch llLS closes, energizing asewing interlock relay. SCR causing sewing head to traverse in a feeddirection. Relay contacts SCR-l and 5CR-3 reverse upon energization ofrelay SCR to energize a clutch and de-energize a brake of a conventionalelectric clutch and brake unit 135 on cam shaft 48. Sewing head feedreleases switch 4LS thereby holding indexing relay 2CR de-energizeduntil the sewing head 10 returns to starting position.

Near the end of the sewing traverse when switch 9L8 is actuated, itcontacts 9LS-l opens and its other contacts 9LS-2 close. However, sewingcycle relay 4CR remains energized, being held in by contacts 6CR-l of awrap cylinder relay 6CR and switch 10LS, a normally open switch heldclosed by a timing cam 134 on cam shaft 48.

After closing of contacts 9LS-2 timing cam 136 actuates switch 12LS uponalignment of needle 50 in trailing saw cut 54 to energize wr'ap cylinderrelay 6CR through a normally closed contact 2CR-2 of indexing relay 2CRwith the wrap cylinder relay 6CR being held in by normally closedcontacts 2CR-2 until indexing relay 2CR is later energized upon returnof sewing head 10 to starting position. Wrap cylinder relay tSCR in turnenergizes solenoid valve 9SOL, through contacts 6CR- 2, which directsair to the needle rod air cylinder 118 to positively thrust needle 50out of its repeating figure 8 pattern into its overwrap position Cbeyond the end sheet of the cleat 22.

With wrap cylinder relay 6 CR energized and upon further angularmovement of cam shaft 48, the cams 60, 88 and 104 drive needle 50alongside the outside end sheet of cleat 22 from position C" intoposition D" and timing cam 134 opens switch IOLS to deenergize sewingcycle relay 4CR and the sewing interlock relay SCR upon opening ofcontacts 4CR-2. Relay SCR reverses the valve solenoids 7SOL and SSOL viarelay contacts 5CR-3 and 5CR-4 controlling the sewing head feed cylinder66 to reverse the direction of the sewing head 10 to return needle 50toward home through leading saw cut 52 of cleat 22 and return switch 9L5to normal position upon disengaging actuator 114. It will be understoodthat switch 10LS may be adjusted so that the brake of the electricclutch and brake unit 135 mounted on cam shaft 48 may be applied at theproper time to ensure alignment of needle 50 with leading saw slot 52through which needle 50 returns.

Upon approaching home, sewing head 10 closes switch 4L5, energizingindexing relay 2CR through contacts 4CR-1, and also energizing valvesolenoid 4SOL which will be understood to undog book clamp 14 through asuitable air cylinder, not shown, and effeet operation of an indexingair clutch, not shown, to index book 16 to the next cleat, if there isone, and also provide a further overwrap on the first sewn end sheet ofcleat 22 and return needle 50 from wrap to sew position by de-energizingthe wrap cylinder relay 6CR. If there are more cleats to be sewn, thesesteps are repeated, but if all cleats have been sewn, the transportslide 18 passes out of the sew station 24 to commence termination of thecleat sewing cycle.

By virtue of the above described construction, the disclosed sewing headoperates to ensure positive overwrap of thread around each cleat of acleat sewn book on both sides of its spine to prevent any undesiredloosening and provide a significantly improved, quality sewn book. Thispositive overwrapping action is ensured in a quick efficient cleatsewingoperation with a minimum number of additional required componentsand by means of a compact unit which can be utilized in either new orexisting machines.

As will be apparent to persons skilled in the art, variousmodifications, adaptations and variations of the foregoing specificdisclosure can be made without de-' parting from the teachings of thepresent invention.

1 claim:

1. A book sewing mechanism for use in progressively lacing thread in arepetitive advancing pattern across a cleat formed by a pair of slitsextending laterally across a spine of a book and comprising a movablespindle, a needle rod having a needle thereon, the needle rod beingmounted on the spindle to be driven thereby, a lost motion drive betweenthe driving spindle and the driven needle rod for driving the needle rodin unison with the spindle laterally of the book spine, and a needle rodactuator for shifting the needle rod relative to the spindle toreposition the needle for thread overwrap in laterally offset relationto the cleat upon sewing of its last end sheet.

2. The mechanism of claim 1 wherein the needle ro d actuator is a powercylinder having an extendible and retractable piston rod drivinglyconnected to the needle rod for positioning the needle relative to thespindle for thread overwrap of the last sewn end sheet of the cleat I 3.The mechanism of claim 1 further including sensing means for sensing thelast end sheet of the cleat, and control means response to the sensingmeans for operating the needle rod actuator upon sewing of the last endsheet of the clcat.

4. The mechanism of claim 3 wherein the sensing means is adjustable forsensing the last end sheet of books of varying thickness.

5. The mechanism of claim 1 wherein the lost motion drive includes a camcontrolled oscillating block, a tubular connector fixed to both theoscillating block and the spindle for moving the spindle laterally ofthe book spine, the needle rod being in telescoping relation to thetubular connector, and a pin and slot lost motion connection between theneedle rod and the tubular connector.

6. The mechanism of claim 5 wherein the needle rod and the tubularconnector are movable between first and second relative positionsrespectively establishing through the pin and slot connection a normalsew position and a thread overwrap position.

7. The mechanism of claim 6 wherein the needle rod actuator includes apower cylinder with a reciprocable piston therein having an extendibleand retractable piston rod coaxially fixed to the needle rod forselectively shifting it between said sew and overwrap positions.

8. The mechanism of claim 7 wherein the power cylinder is normallyde-energized, wherein a spring is received in the power cylinderengaging the piston for biasing the needle rod toward said sew position,and wherein the power cylinder is selectively energizable to overcomethe bias of the spring to reposition the needle in said thread overwrapposition.

9. The mechanism of claim 1 further including a spindle carriage, thespindle being mounted for movement on the spindle carriage in a planeparallel to the spine of the book to be sewn andbeing reciprocablerelative to the carriage both laterally and longitudinally of the spineof the book, the spindle carriage being reciprocable laterally ofthebook spine between a first traversing position, wherein the needle isadjacent a first end sheet of the book to be sewn, and a secondtraversing position wherein the needle is adjacent a last end sheet ofthe book to be sewn, the needle rod actuator being operable for shiftingthe needle rod for thread overwrap when the spindle carriage is in saidsecond traversing position.

10. The mechanism of claim 9 further including a frame, the spindlecarriage being supported on the frame for movement laterally of thespine of the book to be sewn, feed means for driving the spindlecarriage between its first and second traversing positions, the framehaving an adjustable sensor movably mounted on the frame for signalingsewing of the last end sheet of the book, the spindle carriage having alimit switch mounted thereon for actuation by the sensor, and the needleactuator being operable responsive to actuation of the limit switch whenthe needle is disposed in one of said pair of slits to reposition theneedle for thread overwrap.

11. A thread overwrap mechanism usable in a machine for sewing a spineof a book and comprising a spindle carriage, a spindle mounted formovement on the spindle carriage in a plane parallel to the spine of thebook to be sewn and being movable relative to the carriage bothlaterally and longitudinally of the spine of the book, a needle rodmounted on the spindle and having a needle for sewing the book spinebetween its end sheets, the needle rod being movable relative to thespindle between a normal sew position and an extended thread overwrapposition, the spindle carriage being reciprocable laterally of the bookspine between first and second traversing positions wherein the needleis respectively adjacent the first and last end sheets of the book to besewn, means including a power cylinder for moving the needle rodrelative to the spindle, the power cylinder having an extendible andretractable piston rod drivingly connected to the needle rod, the needlerod being movable by the piston rod, when the spindle carriage is insaid second traversing position, to shift the needle from said normalsew position to said extended thread overwrap position to positivelyensure thread overwrap about the last sewn end sheet of the book. I

12. A thread overwrap mechanism usable in a machine for sewing a spineof a book and comprising a spindle carriage, a spindle mounted formovement on the spindle carriage, a needle rod having a needle fixedthereto, the needle rod being supported on the spindle for movementrelative to the spindle and laterally of the spine of the book between anormally retracted sew position and an extended thread overwrapposition, drive means mounted on the spindle carriage and connected tothe spindle for reciprocating the needle rod both longitudinally andlaterally of the spine of the book, feed means for reciprocating thespindle carriage laterally of the book spine between first and secondtraversing positions wherein the needle is respectively adjacent thefirst and last end sheets of the book to be sewn, a lost motion driveconnection between the spindle and needle rod for moving the needle rodrelative to the spindle, and operating means connected to the lostmotion drive for moving the needle rod from its normally retracted sewposition to extended thread overwrap position when the feed means is inits second traversing position to positively drive the needle laterallyof the book spine a sufficient distance to ensure complete threadoverwrap about the last sewn end sheet of the book.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,797,420 Dated March 9.19%

Inventor(s) Daniel I, Streeter It is certified that error appears in theabove-identified. patent and that said Letters Patent are herebycorrected asshown below:

Page 4, line 1, cancel "book spine 23" and substitute therefor --book16- Signed and sealed this l7th day of September 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents uscoMM-oc scan-Poe Y U.S. GOVFRNHEITPRINT IG OFFICE II. OJ$"3)l-

1. A book sewing mechanism for use in progressively lacing thread in arepetitive advancing pattern across a cleat formed by a pair of slitsextending laterally across a spine of a book and comprising a movablespindle, a needle rod having a needle thereon, the needle rod beingmounted on the spindle to be driven thereby, a lost motion drive betweenthe driving spindle and the driven needle rod for driving the needle rodin unison with the spindle laterally of the book spine, and a needle rodactuator for shifting the needle rod relative to the spindle toreposition the needle for thread overwrap in laterally offset relationto the cleat upon sewing of its last end sheet.
 2. The mechanism ofclaim 1 wherein the needle rod actuator is a power cylinder having anextendible and retractable piston rod drivingly connected to the needlerod for positioning the needle relative to the spindle for threadoverwrap of the last sewn end sheet of the cleat.
 3. The mechanism ofclaim 1 further including sensing means for sensing the last end sheetof the cleat, and control means response to the sensing means foroperating the needle rod actuator upon sewing of the last end sheet ofthe cleat.
 4. The mechanism of claim 3 wherein the sensing means isadjustable for sensing the last end sheet of books of varying thickness.5. The mechanism of claim 1 wherein the lost motion drive includes a camcontrolled oscillating block, a tubular connector fixed to both theoscillating block and the spindle for moving the spindle laterally ofthe book spine, the needle rod being in telescoping relation to thetubular connector, and a pin and slot lost motion connection between theneedle rod and the tubular connector.
 6. The mechanism of claim 5wherein the needle rod and the tubular connector are movable betweenfirst and second relative positions respectively establishing throughthe pin and slot connection a normal sew position and a thread overwrapposition.
 7. The mechanism of claim 6 wherein the needle rod actuatorincludes a power cylinder with a reciprocable piston therein having anextendible and retractable piston rod coaxially fixed to the needle rodfor selectively shifting it between said sew and overwrap positions. 8.The mechanism of claim 7 wherein the power cylinder is normallyde-energized, wherein a spring is received in the power cylinderengaging the piston for biasing the needle rod toward said sew position,and wherein the power cylinder is selectively energizable to overcomethe bias of the spring to reposition the needle in said thread overwrapposition.
 9. The mechanism of claim 1 further including a spindlecarriage, the spindle being mounted for movement on the spindle carriagein a plane parallel to the spine of the book to be sewn and beingreciprocable relative to the carriage both laterally and longitudinallyof the spine of the book, the spindle carriage being reciprocablelaterally of the book spine between a first traversing position, whereinthe needle is adjacent a first end sheet of the book to be sewn, and asecond traversing position wherein the needle is adjacent a last endsheet of the book to be sewn, the needle rod actuator being operable forshifting the needle rod for thread overwrap when the spindle carriage isin said second traversing position.
 10. The mechaNism of claim 9 furtherincluding a frame, the spindle carriage being supported on the frame formovement laterally of the spine of the book to be sewn, feed means fordriving the spindle carriage between its first and second traversingpositions, the frame having an adjustable sensor movably mounted on theframe for signaling sewing of the last end sheet of the book, thespindle carriage having a limit switch mounted thereon for actuation bythe sensor, and the needle actuator being operable responsive toactuation of the limit switch when the needle is disposed in one of saidpair of slits to reposition the needle for thread overwrap.
 11. A threadoverwrap mechanism usable in a machine for sewing a spine of a book andcomprising a spindle carriage, a spindle mounted for movement on thespindle carriage in a plane parallel to the spine of the book to be sewnand being movable relative to the carriage both laterally andlongitudinally of the spine of the book, a needle rod mounted on thespindle and having a needle for sewing the book spine between its endsheets, the needle rod being movable relative to the spindle between anormal sew position and an extended thread overwrap position, thespindle carriage being reciprocable laterally of the book spine betweenfirst and second traversing positions wherein the needle is respectivelyadjacent the first and last end sheets of the book to be sewn, meansincluding a power cylinder for moving the needle rod relative to thespindle, the power cylinder having an extendible and retractable pistonrod drivingly connected to the needle rod, the needle rod being movableby the piston rod, when the spindle carriage is in said secondtraversing position, to shift the needle from said normal sew positionto said extended thread overwrap position to positively ensure threadoverwrap about the last sewn end sheet of the book.
 12. A threadoverwrap mechanism usable in a machine for sewing a spine of a book andcomprising a spindle carriage, a spindle mounted for movement on thespindle carriage, a needle rod having a needle fixed thereto, the needlerod being supported on the spindle for movement relative to the spindleand laterally of the spine of the book between a normally retracted sewposition and an extended thread overwrap position, drive means mountedon the spindle carriage and connected to the spindle for reciprocatingthe needle rod both longitudinally and laterally of the spine of thebook, feed means for reciprocating the spindle carriage laterally of thebook spine between first and second traversing positions wherein theneedle is respectively adjacent the first and last end sheets of thebook to be sewn, a lost motion drive connection between the spindle andneedle rod for moving the needle rod relative to the spindle, andoperating means connected to the lost motion drive for moving the needlerod from its normally retracted sew position to extended thread overwrapposition when the feed means is in its second traversing position topositively drive the needle laterally of the book spine a sufficientdistance to ensure complete thread overwrap about the last sewn endsheet of the book.